This invention relates to a luminaire having means for containing hot particles of lamp components produced by the unlikely event of the lamp rupture. More particularly, this invention relates to a mesh interposed between a pressurized lamp and a refractor lens or globe of a flammable material of the luminaire for intercepting and capturing the hot particles that may be dislodged from the pressurized lamp under the unlikely rupture condition and which particles are of a sufficient temperature and heat capacity to cause excessive heat damage to the luminaire.
As disclosed in U.S. patent application Ser. No. 047,813 filed May 8, 1987 now abandoned of C. A. Willis assigned to the same assignee as the present invention, lamps under a pressurized condition, such as metal halide and tungsten-halogen lamps may experience a rupture condition. These pressurized lamps, and in particular, metal halide discharge lamps may experience the rupture condition which causes hot flying fragments to be dislodged from the lamp. Lamp failures which occur in such a manner are infrequent and although incidences of such failures are extremely minor, there is no practical way known at this time to completely eliminate the possibility of such failures.
One way of minimizing such failures in continuously operating systems is to turn the lamps, in particular the metal halide lamps, off once a week for about 15 minutes. If this procedure is followed, those lamps approaching the end of their life will either probably fail to restart before reaching a point where a chance for a non-passive rupture failure begins to increase or the failure will occur due to the arc related to the metal halide lamp being unable to withstand the thermal stresses during warm-up and the arc will fail at a low, relatively non-destructive pressure. Replacing lamps at or before the end of their rated life will also decrease the possibility of non-passive rupture failures. Another way to minimize the possible hazards associated in the unlikely event of an arc tube rupturing, is to operate the lamp in a fixture designed to contain such a failure, such as a fixture comprising a refractor or lens made of a tempered safety glass.
Glass enclosures such as tempered safety glass lenses while serving as means for containing a ruptured arc tube do not have the benefits of plastic materials. For example, plastic materials due to their weight and non-fracture characteristics avoid the hazards of having heavy chunks of borosilicate glass comprising a lens falling from luminaires that may be located in factories. Further, the light weight plastics, such as acrylic, may be more accurately molded to provide superior optical features relative to those yielded by glass. In the unlikely event of a catastrophic failure caused by the bursting of the arc tube of the metal halide lamp, it is possible for hot shards of a quartz arc tube to impinge or otherwise fall directly onto the acrylic or other flammable plastic lens or refractor which may result in burning hot plastic from the lens or refractor dripping down onto the environment located under the related luminaire. It is desired that means be provided within the luminaire to substantially reduce or even eliminate the related heat damage to the luminaire by capturing and containing any hot particles that have the potential to ignite the flammable lens or refractor of the luminaire.
Accordingly, it is an object of the present invention to provide containment means for a luminaire which largely eliminates the risk of igniting the flammable plastic lens or refractors and its related secondary fire risks.